Two days ago, Anastasia was 14 years old. Next year she will turn 17. What is today's date, how old is she today, and when was her birthday?
Solution
Making a chart can help, like the one in part A of the figure below. Then think hard about how to match up the scanty facts with a calendar. If she will turn 17 year, then she must turn 16 year and must have turned 15 year. But two days ago she was still 14! So her birthday must be Dec. 31, the last day of the year and she is talking on the next day which happens to be in the next year, as depicted in part B of the figure.
The initial impulse---to think that Leap Year is involved---turns out to be false.
